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Plug-in hybrid cars release almost five times greater planet-heating pollution than official figures show, as per a recent report.

Growing Discrepancy Between Lab and Actual Emissions

Data shows that PHEVs emit only 19% lower CO₂ than traditional gas and diesel vehicles, based on research carried out by a non-profit group. That differs sharply with lab tests, which assumed a 75% decrease in pollution.

Researchers studied information from in-vehicle energy use monitors of 800,000 vehicles sold in Europe from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” stated a lead analyst participating in the study. “This gap is growing and poses a significant problem. Consequently, PHEVs pollute nearly as heavily as petrol cars.”

Key Factors Driving the Emissions Gap

Researchers linked the majority of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in battery mode compared to total distance. They found that just a quarter of driving was completed in electric mode, whereas lab assumptions suggested 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than official estimates. This occurred because EV motors were not strong sufficient to operate independently, leading to engines using gasoline for almost a third of the travel completed in electric mode.

Regulatory and Financial Consequences

According to calculations, the underestimation of PHEV CO2 output enabled four major carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could pay about €500 extra annually in operating costs than is estimated under lab conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the truth,” commented a automotive expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the environment and saving money. Actually, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Pressure

Hybrid vehicles have recently been brought back into political discussions as automakers have lobbied the European Union to weaken CO₂ targets. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from member states with large automotive industries.

Some high-level politicians have suggested PHEVs as a potential “flexibility” solution to introduce in the legislation.

One independent energy economics specialist, who was not involved with the study, called the report a “highly valuable contribution” after years in which segments of the automotive sector argued there was too little information to properly assess actual CO2 output.

“The results demonstrate, without question, that the difference in lab and real-world PHEV fuel consumption and CO₂ output is much, much greater than for petrol or conventional vehicles,” they stated. “All policy adjustments concerning PHEVs should be made with extreme caution and in the light of this data.”